The Physics of the Curveball – A Short History

The charm of the National Pastime is in part due to the myths it inspires, from the creation story of Abner Doubleday, to the beginnings of the curveball and William Cummings. “Candy” Cummings claimed to have invented the curve in 1863 after noticing thrown clam shells bobbed and dipped in flight. What a delightful story! Of course, like Doubleday’s invention of baseball, Cummings’ claim to the first curveball is subject to dispute.

The debate about whether the ball actually curved or just appeared to do so probably began as soon as the first batter came back to the bench after being struck out by the mighty deuce. These arguments were mainly a barroom diversion until May 1941 when R. W. Madden’s letter to the editor of the New Yorker asserted, “No man alive, nor no man that ever lived, has ever thrown a curve ball. It can’t be done.”

The firestorm of follow-up letters to the editor likely gave birth to the famed investigation Life magazine published on Sept. 15, 1941. In the article entitled, “Baseball’s Curve Balls: Are They Optical Illusions?” Life used photographs of Cy Blanton’s and Carl Hubbell’s curves to conclude, “a baseball is so heavy an object . . . that the pitcher’s spinning action appears to be insufficiently strong appreciably to change its course.”

Life’s article prompted the first published experimental study of curveballs by physicists. Frank Verwiebe of Eastern Illinois Teachers College published the note, “Does a Baseball Curve?” in the American Journal of Physics (AJP) in April 1942. Verwiebe followed the trajectory of a curve by having a pitcher throw the ball through five screens made of light thread. The broken strands revealed the gross features of the path of the ball. His data clearly showed a variation between the trajectory of a curveball and the track of a ball solely under the influence of gravity. In August of the same year Richard Sutton of the University of Minnesota published his note, “Baseballs Do Curve and Drop!” also in AJP. He did a more detailed analysis of Life’s photographs to dispute their conclusion.

These scientific investigations might have ended the discussion, but in its July 19, 1949 issue, Look magazine published “Visual Proof that a Baseball Curves.” Look used flash photography of Cub pitcher Johnny Schmitz to deduce, “there is no such thing as a ‘straight’ ball.” Perhaps to correct for its earlier transgressions or maybe just to keep pace with the competition, Life published “Camera and Science Settle the Old Rhubarb About Baseball’s Curve Ball” in its July 27, 1953 issue. This article not only showed that curveballs curve, but added a new dimension to the debate by concluding the baseball does curve, but not suddenly. Now that the curve of the curveball was an established fact, a new can of worms seemed to be opening — is the curvature gradual or is there a sudden “break”?

The first wind tunnel measurements of spinning baseballs were published in AJP in 1959 by Lyman J. Briggs the third director of the National Institute of Standards and Technology. “Effect of Spin and Speed on the Lateral Deflection (Curve) of a Baseball; and the Magnus Effect for Smooth Spheres” predicted, “When applied to a pitched ball in play, the maximum expected curvature ranges from 10 to 17 inches.” In his 1990 book, “The Physics of Baseball,” Robert Adair used Briggs’ results to categorically state, “Does a curve ball then travel in a smooth arc like the arc of a circle? Yes. Does the ball ‘break’ as it nears the plate? Yes. Neither the smooth arc nor the break is an illusion but a different description of the same reality.”

With the trajectory matter settled, the work that remained involved the deep details of the physics such as lift coefficients. Leroy Alaways’ Ph.D. thesis “Aerodynamics of the Curve-Ball: An Investigation of the Effects of Angular Velocity on Baseball Trajectories” addressed this issue and contains a much more detailed history of the curveball. Currently, the final say on the flight of pitches is Alan Nathan’s paper “The effect of spin on the flight of a baseball” published in AJP in 2008. The theory of the flight of the curve has been verified for the most part with the precise trajectory data from Major League Baseball’s PitchFX system.

Yet, the persistence of myth is central to the human condition and so it is in baseball. There are still those that insist the curve doesn’t curve. They often cite the 2009 Illusion of the Year. The appropriate punishment for the stubborn adherents of the discredited letter-to-the-editor writer, Mr. Madden, was once suggested by Hall of Fame pitcher Dizzy Dean: “Shucks, get behind a tree and I’ll hit you with an optical illusion.”

Print Friendly
 Share on Facebook12Tweet about this on Twitter8Share on Google+0Share on Reddit0Email this to someone
« Previous: Punishing Kids for Breaking a Rule No One Follows
Next: Dick Green at the Hall »


  1. said...

    Nice article, Dave. Actually, I never understood why anyone who has ever played golf would be skeptical of a curve ball. Slices and hooks are pretty common in golf, and while the numerical details might be a little different in baseball, the underlying physics is all the same. But, then again, one thing that physicists like to think they are good at is seeing similarities among seemingly diverse systems.

  2. said...

    Sadly for golfers like me, you are exactly right. I’ve hit some hooks and slices that truly dazzle my partners. But I think your tacit assumption that baseball players look at things through the same rose-colored glasses as physicists do more than likely accounts for their different viewpoints–not the underlying physics!.

  3. losealot said...

    just wanted to mention that my slices also have a “sudden” break — i tend to break my club when i hit one!

  4. Garden Weasel. said...

    Not a golfer , but popping in to state the obvious –
    Golf balls are dimpled. The dimpling affects the spin and curve.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>